The present invention relates generally to a galvanic cell with at least one electrode whose active material consists of a conductive, organic polymer compound of polyconjugated structure which can be doped with cations or anions, and which has an aluminum charge eliminator.
Electricity-conducting organic polymers are capable of being formed from the corresponding monomers. Depending on the conditions of their formation, the end products are more or less deep-colored crystalline powders or films which form a film-like coating on the wall of the reaction vessel. Such end products can be separated from the liquid reaction medium, generally a suspension of a Ziegler-Natta catalyst in an organic solvent, and then molded and processed in a simple manner after purification.
Despite their good intrinsic conductivity, in using these materials as electrode materials in a polymer cell it has previously been common practice to provide such materials (e.g., a (CH).sub.x film) with a metal wire (e.g., a Pt wire) to serve as a current collector, and to thus improve the performance capacity of the electrode. Since the connection with the metallic charge eliminator is brought about solely by mechanical pressure, this current collector remains unsatisfactory because of inevitable contact resistance, even in the case of flat charge eliminator materials. This in turn reduces the potential of the loaded electrode.
Efforts have therefore recently been made to provide for a chemical or physical-chemical binding of the polymer material to the metallic charge eliminator, which offers the advantage of having a lower contact resistance. Such measures include, for example, the application of metallic charge eliminators on a layer-shaped polymer structure by vapor deposition or sputtering, or by applying a conductive layer on the polymer surface by photographic techniques. However, in such cases, it has been found that surges in the capacity of the polymer during a charge-discharge cycle can burst the vapor-deposited or printed charge eliminator layer.
Many conducting polymers are formed from monomers by oxidation, in which process radical ions are formed which then undergo dimerization. The dimers are oxidized to a polymer chain via oligomeric intermediate units by adding monomer units. For example, it is known from DE-OS No. 33 26 193 that such a polymer synthesis can be carried out directly on a porous metal body, which serves as the substrate for the deposition and for the further growth of the polymer. The metal body thus becomes both the supportive skeleton and the charge eliminator for the organic electrode material upon its activation by subsequent doping. However, in view of the fact that some polymers are characterized by very high oxidation potentials, relatively corrosion-resistant metals such as nickel, nickel-chromium, copper, copper-nickel, silver or platinum are used as the carrier skeleton.
Conversely, according to JP-OS No. 59-12576 (DE-OS No. 33 24 968), aluminum has been vacuum-deposited on a leaf-shaped polyacetylene material, whereupon the metal-coated polymer is subjected to recoil ion implantation. In this process, because of their high kinetic energy, aluminum atoms penetrate into the conductive polymer and produce a diffuse transition layer between the polymer and the metal substrate, so that a firm connection with low contact resistance is obtained.
The volume-related theoretical energy density of polymer systems is relatively low, a disadvantage which is even more evident when such polymer cells are used in practice. This is because most of the known electrode carriers represent a disproportionately large dead volume as compared with the applied polymer layer, which has a thickness of only a few .mu.m. Consequently, the volume-specific energy densities of polymer electrodes used in practice are far below their theoretical value.